Method and system for energy management and overspeed protection of a centrifuge

Abstract

A method for limiting an operating speed of a centrifuge rotor includes the steps of determining whether an actual parameter value of the rotor is within a predetermined range of an expected parameter value of the rotor, and limiting the operating speed when the actual parameter value is not within the predetermined range of the expected parameter value. At least one of the following parameters is evaluated: (i) energy required to accelerate the rotor from rest to a predetermined speed, (ii) change in energy required to accelerate the rotor from a first speed to a second speed, (iii) energy loss due to windage of the rotor, (iv) time required to accelerate the rotor from a first speed to a second speed, (v) speed of the rotor at a predetermined time, and (vi) ratio of drag coefficient and inertia.

What is claimed is:  
     
       1. A method for limiting an operating speed of a rotor installed in a centrifuge system, comprising: 
       (a) determining whether an actual ratio of drag coefficient and inertia of said rotor is within a predetermined range of an expected ratio of drag coefficient and inertia; and  
       (b) limiting said operating speed when said actual ratio is not within said predetermined range of said expected ratio.  
     
     
       2. The method according to  claim 1 , wherein step (a) comprises: 
       (a1) receiving a rotor identification; and  
       (a2) determining, from said identification, said expected ratio.  
     
     
       3. The method according to  claim 2 , wherein step (a2) comprises looking up said expected ratio in a table indexed by said identification. 
     
     
       4. The method according to  claim 1 , wherein step (a) comprises: 
       (a1) determining a first differential acceleration (drpm 1 /dt 1 ) for a first speed (rpm 1 ); and  
       (a2) determining a second differential acceleration (drpm 2 /dt 2 ) for a second speed (rpm 2 ).  
     
     
       5. The method according to  claim 4 , wherein said actual ratio includes: 
       a first term of 2π[(drpm 2 /dt 2 )−(drpm 1 /dt 1 )]; and  
       a second term of 60[(rpm 1 /1000) 1.8 −(rpm 2 /1000) 1.8 ].  
     
     
       6. The method according to  claim 4 , wherein step (a) includes the steps of: 
       (a1) determining a first discrete speed (rpm 1     1   ) marginally below said first speed (rpm 1 ), and a time (time 1     1   ) at which said first discrete speed (rpm 1     1   ) occurred;  
       (a2) determining a second discrete speed (rpm 1     2   ) marginally above said first speed (rpm 1 ), and a time (time 1     2   ) at which said second discrete speed (rpm 1     2   ) occurred;  
       (a3) determining a third discrete speed (rpm 2     1   ) marginally below said second speed (rpm 2 ), and a time (time 2     1   ) at which said third discrete speed (rpm 2     1   ) occurred; and  
       (a4) determining a fourth discrete speed (rpm 2     2   ) marginally above said second speed (rpm 2 ), and a time (time 2     2   ) at which said fourth discrete speed (rpm 2     2   ) occurred.  
     
     
       7. The method according to  claim 6 , wherein said actual ratio includes: 
       a first term of  
       
         
           2π[(rpm 2     2   −rpm 2     1   )/(time 2     2   −time 2     1   )−(rpm 1     2   −rpm 1     1   )/(time 1     2   −time 1     1   )] 
         
       
       and 
       a second term of 60[(rpm 1 /1000) 1.8 −(rpm 2 /1000) 1.8 ].  
     
     
       8. The method according to  claim 1 , wherein step (b) comprises looking up a maximum speed in a table indexed by said actual ratio.